The embodiments described herein relate generally to operating a power conversion system, and more specifically, to controlling the power conversion system to provide a predefined power to an electrical grid.
Solar energy has increasingly become an attractive source of energy and has been recognized as a clean, renewable alternative form of energy. Solar energy in the form of sunlight may be converted to electrical energy by solar cells. A more general term for devices that convert light to electrical energy is “photovoltaic cells.” Solar cells are a subset of photovoltaic (PV) cells.
In order to obtain a higher current and voltage, solar cells are electrically connected to form a solar module. In addition to a plurality of solar cells, the solar module may also include sensors, for example, an irradiance sensor, a temperature sensor, a voltage meter, a current meter, and/or a power meter. Solar modules may also be connected to form a module string. Typically, the direct current (DC) voltages output by the module strings are provided to a power converter, for example, a DC to alternating current (AC) voltage inverter. The DC to AC voltage inverter converts the DC voltage to three-phase AC voltage or current. The three-phase AC output from the DC to AC inverter is provided to a power transformer, which outputs a three-phase high-voltage AC power to an electrical grid. An AC contactor selectively electrically couples the power converter and the electrical grid.
Typically, an operator of a power generation system coupled to an electrical grid agrees to supply the electrical grid with a defined level of power. It is financially beneficial for the operator to supply power to the electrical grid for as much of each day as possible. As the sun rises, the PV array voltage increases. Once the PV array voltage reaches a predefined level, the power converter is activated, the AC contactor is closed to couple the power converter and the electrical grid, and the power generation system attempts to supply power to the electrical grid. If the PV array is not able to provide the defined level of power, for example, if the irradiance level is not high enough to support the defined level of power, the AC contactor is opened, which disconnects the power converter from the electrical grid. Typically, the AC contactor remains open for a predefined length of time before it is closed to once again attempt to supply power to the electrical grid. This process is repeated until the PV array is able to support the defined level of power. A similar process may be repeated as the sun sets. The cycling on and off of the AC contactor causes wear and reduces the useful life of the AC contactor.